1. Field of the Invention
The present invention relates to aquatic plant harvesters, and in particular but not solely to weed harvesters for use in preparation and maintenance of lake and waterway shallow marine sporting facilities. The invention may also be useful in commercial aquatic plant harvesting, marine and fresh water.
2. Summary of the Prior Art
Preparation and maintenance of lake and waterway sports facility includes the requirement to harvest and remove submerged and floating aquatic plants. The governing rules of certain sporting bodies require complete clearance to specified minimum depths. For example the International Rowing Body FISA requires a clear water zone to a depth of 3 metres below the hull of the racing craft.
Plants requiring control in Australian facilities include but are not limited to: Potamogeton ochreatus, P. tricarinatus, P. perfoliatus, P. crispus, Myriophyllum verrucosum, Hydrilla verticillata, Vallisneria americana, Egeria densa, Water Milfoil, Canadian Pondweed, Salvinia and Typha. 
There are several existing barge or punt mounted marine harvesters intended for use in this area. These include the Aqua-Equip harvester manufactured by the Attosar Corporation of Oatville Ontario Canada. This machine includes a barge with an angled conveyor extending into the water from its leading edge. The angled conveyor is formed of an open chain grid. A cutting head is provided at the lower submerged end of the angled conveyor to cut marine weed. The weed is intended to float onto the conveyor and be conveyed up to a catchment trough. Entrained water spills through the open grid of the conveyor as it is carried from the water. Similar arrangements are also used in the other vessels that the applicants are aware of.
Experience has shown that these arrangements provide inefficient collection of the cut weed leaving large quantities of floating vegetative material. Also, with many exotic weeds the weeds will propagate from severed nodes. The severed nodes are relatively small and prone to falling through the open conveyor grids. These disadvantages have generally required the use of additional surface clean up vessels. These clean up vessels may operate during and after harvesting, pulling or pushing a scoop net through the surface region to remove remaining vegetable material.
Another difficulty is that these harvesters create a significant bow pressure wave when moving forward at reasonable speeds. The inventors believe this is due to the large frontal area defined by the conveyor. Pressure waves can cause redistribution of plant material leading to large amounts left uncut. This reduces the effective operating speed of the harvester.